Beam load cell stress measurement devices are well-known in the art. FIG. 1 illustrates a simplified model of a conventional beam load cell 100. In this model, load cell 100 consists of a fixed first part 110, a moveable second part 120 and measurement component, referred to as load-beam, 130 therebetween. Measurement component 130 further includes measurement resistors 140 thereon. The resistors may be piezoresistors or other devices. The resistors 140 change resistance value in accordance with the magnitude of an applied force or stress.
As force 145 is applied to load cell 100, the second part 120 moves in accordance with the applied force, and measurement component 130 is stressed in response. Beam type transducers are known in the prior art and it is known how to limit the deflection. See U.S. Pat. No. 4,051,451 entitled, “Beam Type Transducers Employing Dual Direction Limiting and Means”, which issued on Sep. 27, 1977 to A. D. Kurtz et al and is assigned to Kulite Semiconductor Products, Inc., the assignee herein. That patent shows a beam subjected to a transverse force (up and down) to move the beam with a stop above and below the beam.
See also U.S. patent application Ser. No. 09/814,903 entitled, “Force Transducer with Environmental Protection” filed Mar. 22, 2001 for A. D. Kurtz et al. and assigned to the assignee herein. This application shows a beam load cell as utilized herein.
In the load cell transducer, as shown in FIG. 1, as one can ascertain, if unusually large forces are applied in either a pull or a push direction, the beam can fracture and actually come apart. In this manner, it can cause catastrophic failure of the entire system. For example, one may want to measure the stresses applied on an aircraft rudder during a mission or during normal operation. One may use the pressure sensor as part of a servo system, where as the pressure increases, one may want to turn the rudder or apply more or less force on the rudder. If the beam fractures, then the entire sensor becomes inoperable and therefore, there would be no recovery of the control system. However, if the beam is stopped and prevented from rupturing or fracturing, then when normal forces are applied, the sensor will still operate during normal operation and thus, a disaster can be circumvented. In this manner, there is provided a new and improved load cell which employs a stop to prevent the rupture or breakage of a beam employed for measuring forces in either a push or a pull direction.